1. Field of the Invention
The present invention relates in general to a pedestrian protection apparatus for a vehicle, more particularly, to an improved structure of the pedestrian protection apparatus installed at a lower part of a front face of the vehicle and arranged to sweep a lower parts of the leg portion that has collided with or came into contact with the front face of the vehicle, thereby protecting the leg portion of the pedestrian.
2. Discussion of Related Art
Various types of protection apparatuses are conventionally installed at a front, a rear, or side faces of the vehicles such as automotive vehicles, mainly in order to absorb an impact energy generated upon a collision, for thereby protecting the bodies of the vehicles and vehicle passengers. In recent years, apparatuses for protecting pedestrians have been installed at the front of vehicle to protect the pedestrian when the front of the vehicle collides with or comes into contact with the pedestrian.
As one type of a pedestrian protection apparatus, there is known a so-called leg-sweep apparatus. The leg-sweep apparatus is installed inside of a front bumper or at a lower part of the front bumper independently of the front bumper. The leg-sweep apparatus is arranged to apply a counterforce with respect to an impact load, which is inputted upon a collision of the pedestrian with the front face of the vehicle, to the lower part of the leg portion of the pedestrian so that the lower part of the leg portion is swept (scooped up) and the pedestrian falls down toward the vehicle. Thus, it is possible to minimize the occurrence of injuries such as a bone fracture of the leg portion, thereby assuring protection and safety of the pedestrian.
For example, a patent publication document 1 (JP-A-2001-277963) discloses a leg-sweep apparatus which is arranged to be disposed at the lower part of the front of a vehicle and includes; a resin foam body which extends in a width direction of the vehicle such that at least a part thereof protrudes from the front face of the vehicle, and a beam which extends in the width direction of the vehicle while being in contact with the back side of the resin foam body. A patent publication document 2 (JP-A-2004-25976) discloses a leg-sweep apparatus that is formed of, for example, a metal pipe, and that is fixed to the lower part of the front of a vehicle such as to extend in the width direction of the vehicle. Further, a patent publication document 3 (JP-A-2004-203183) discloses a leg-sweep apparatus which includes; a plate member which extends in the frontward and backward direction of a vehicle and fixed to the lower part of the front of the vehicle; and a plurality of flat ribs disposed on a front portion of the plate member so as to extend upright therefrom, so that the front portion of the plate member has an increased rigidity. Further, a rear portion of the plate member has a flat plate-like configuration extending in the frontward and backward direction of the vehicle. The thus constructed apparatus is fixed to the vehicle at a rear-side end section of the rear portion of the plate member. However, the leg-sweep apparatus disclosed in the above publications have backwards disadvantages which should be rectified.
That is, the pedestrian protection apparatus disclosed in the patent publication document 1 needs a large number of components. For this reason, the component cost is inevitably high, and it is cumbersome to install the apparatus on the vehicle. The pedestrian protection apparatus disclosed in the patent publication document 2 inevitably has a large weight, and it is difficult to form the apparatus in a shape that conforms to the shape of the front face of the vehicle.
The pedestrian protection apparatus disclosed in the patent publication document 3 ensures a sufficiently reduced weight where the plate member and the plurality of ribs are formed integrally with each other using a synthetic resin material, for instance. Moreover, a higher formability and a smaller number of components can be advantageously achieved by employing, in formation of the plate member and the plurality of ribs, a molding technique using metal dies such as injection molding. This effectively eliminated the disadvantages of the pedestrian protection apparatuses disclosed in a patent publication document 1 and 2. However, further enhancement of the impact performance is hindered by some obstacles described below.
Namely, in the pedestrian protection apparatus disclosed in the patent publication document 3, an impact load in the load characteristic is promptly increased and reaches a target value quickly when the apparatus contacts with the leg portion of a pedestrian, thus ensuring high impact performance that permits a high degree of sufficient counterforce with respect to the impact load to be instantaneously exhibited. To this end, it is necessary to increase the height of the ribs provided in the front portion of the plate member, to which the impact load is inputted, so that the front portion has a sufficient rigidity, for thereby preventing the front portion from being easily deformed. In this case, however, even when the apparatus is constituted by a resin-molded product, the total weight of the pedestrian protection apparatus is increased by the increase in height of the ribs, and the merit of resin-molded product, i.e. lightness is considerably deteriorated. Further, where the height of the each rib is increased, it is required to form sufficiently deep recesses in a molding die for forming each rib having increase height. Therefore, it takes additional time to form the metal mold, and release characteristics of the molded component may be deteriorated. In consequence, there may be caused a problem of deterioration in manufacturing efficiency of the entire pedestrian protection apparatus.
Under the situations mentioned above, a patent publication document 4 (JP-A-2002-264741) discloses a pedestrian protection apparatus in which, instead of the flat ribs, a plurality of reinforcing beads are provided integrally on a front portion of a plate member. Each reinforcing bead extends in the frontward and backward direction of the vehicle with an angular U-shaped cross section or channel-like configuration in the vehicle width direction that is open downward. With this configuration, while the protrusion heights of the reinforcing beads are relatively small, the front portion of the plate member can have a rigidity that is equivalent to the rigidity obtained when the high flat ribs are formed integrally on the front portion of the plate member. Accordingly, the disadvantages of the pedestrian protection apparatuses disclosed in the patent publication documents 1 and 2 can be eliminated, and furthermore, the problem of the pedestrian protection apparatus disclosed in the patent publication document 3 can be eliminated.
However, as the result of various tests and investigations, the inventors of the present invention found that the pedestrian protection apparatus disclosed in the patent publication document 4 had following problems. That is, in this apparatus, since all the angular U-shaped reinforcing beads protrude upward from the front portion of the plate member, there is a difference in rigidity between an upper side and a lower side of the plate member. Therefore, a force for lifting up the plate member inevitably acts on the front portion of the plate member upon inputting of the impact load. The rear portion of the flat plate member is relatively easily bent so that the front portion of the plate member is curled up. As a result, the rise of the impact load in the load characteristic is delayed, and the impact load cannot instantaneously reach the target value. In consequence, the high rigidity is ensured in the front portion of the plate member, but the pedestrian protection apparatus disclosed in the patent publication document 4 does not ensure satisfactory impact performance that permits a sufficiently high degree of counterforce with respect to the impact load to be instantaneously exhibited.
When the pedestrian protection apparatus disclosed in the patent publication document 4 is installed on the lower part of the vehicle, the rear ends of the reinforcing beads are in contact with a cross member of the vehicle. Therefore, when an impact load is inputted, a counterforce thereto can be effectively obtained from the cross member via the reinforcing beads. However, when an impact load is not generated by a collision with the pedestrian, but is generated by, for example, a low-speed collision, a so-called light collision, with a solid structure such as a wall, a heavy impact load is inputted to the cross member via the reinforcing beads. Thereby, the cross member is damaged heavily. As a result, even if the collision is light, high repair cost is required. This was also found by the inventors of the present invention.